Nanotribology of a vapor-phase lubricant: A quartz crystal microbalance study of tricresylphosphate (TCP) uptake on iron and chromium

Adsorption measurements of tricresylphosphate (TCP) on high-purity iron and chromium surfaces have been performed in ultra-high vacuum with a quartz crystal microbalance in conjunction with Auger electron spectroscopy, yielding values for gas uptake rates, molecular slippage, and tribofilm stress levels in the temperature range 25-400degreesC. At room temperature, TCP uptake is observed to be limited to two layers of intact molecules that are likely to be physisorbed. Above 200degreesC, the data recorded on both iron and chromium substrates are consistent with far greater uptake levels and extensive interdiffusion of TCP fragments with the substrate. The most noteworthy difference between the two substrates is TCP's fragmentation upon impact on iron, but not chromium, at elevated temperatures.